African Water Development Report 2006 - United Nations Economic ...

African Water Development Report 2006Pressures on Freshwater Ecosystems – The World OutlookA wide range of human uses and transformations of freshwater or terrestrial environments can alter,sometimes irreversibly, the integrity of freshwater ecosystems.Human Activity Potential Impact Function at RiskPopulation and consumption growthInfrastructure development (dams,dikes, levees, diversions)Land conversion eliminates keycomponents of aquatic environment,loss of functions, integrity,habitat & biodiversity, alters runoffpatterns, inhibits natural recharge,fills water bodies with siltOverharvesting and exploitationIntroduction of exotic species:Outdoes competition of native species,alters production and nutrientcycling, loss of biodiversityRelease of pollutants to land, air orwaterIncreases water abstraction andacquisition of cultivated land throughwetland drainage. Increases requirementfor all other activities withconsequent risksLoss of integrity alters timing andquantity of river flows, watertemperature, nutrient and sedimenttransport and thus delta replenishment,blocks fish migrationsNatural flood control, habitats forfisheries and waterfowl, recreation,water supply, water quantity andqualityDepletes living resources, ecosystemfunctions and biodiversity(groundwater depletion, fisheriescollapse)Food production, wildlife habitat,recreationPollution of water bodies alterschemistry and ecology of rivers,lakes and wetlands. Greenhouse gasemissions produce dramatic changesin runoff and rainfall patternsVirtually all ecosystem functionsincluding habitat, production andregulation functionsWater quantity and quality, habitats,floodplain fertility, fisheries, deltaeconomiesFood production, water supply,water quality and water quantityWater supply, habitat, water quality,food production. Climate changemay also affect hydropower, dilutioncapacity, transport, flood controlSource: UNESCO WWDR, 2003 (Extracted from the Executive Summary of the WWDR. IUCN, 2000. Vision for Water and Nature. A World Strategyfor Conservation and Sustainable Management of Water Resources in the 21st Century - Compilation of All Project Documents. Cambridge).152